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Friday, November 7, 2008

Corvids Part IV - Western Scrub-Jay

The species formerly known as "Scrub Jay" has been broken into three separate species, of which theWestern Scrub-Jay (also known as the California Jay or Long-tailed Jay), is one. This species can be devided into three additional forms…which may or may not be separate species; the Mexican Jay is one.

This jay’s tail is noticably longer than the Steller’s and it lacks a crest. It is dark blue overall with pale grey or whitish underparts and a dark grey cheek and bright blue necklace. Internally based species are more pale than island species and costal species. There is a narrow whitish line over it’s eye.

In addition to urban gardens, Scrub-Jays inhabit areas of low scrub; especially pinyon-juniper forests, oak woods and sometimes mesquite bosques where, feeding in pairs and family groups, they feed on frogs and lizards, eggs and young birds, insects and in wintertime, grains, nuts and berries. This bird is non-migratory andwill come to bird feeders and campsights where it can become quite tame.

Western Scrub-Jays, like many other corvids, exploit food surpluses by storing food in caches scattered within their territories. In the process of collecting and storing this food, western scrub-jays have shown an ability to plan ahead in choosing cache sites to provide adequate food volume and variety for the future. Because of their excellent observational spatial memories, they will steal food from other birds caches. To protect their caches from potentials thieves, they implements a number of strategies to reduce this risk of theft.

The Western Scrub-Jay has been used in laboratory studies of its ability to hide (cache) and remember seeds. Jays that had stolen the caches of other jays noticed if other jays were watching them hide food. If they had been observed, they would dig up and hide their food again. Jays that had never stolen food did not pay any attention to whether other jays were watching them hide their food.

The Western Scrub-Jay feeds on parasites on the body of mule deer, hopping over the body and head of the deer to get them. The deer often help the jays by standing still and holding their ears up. Oddly, Western Scrub-Jays in areas where acorns are abundant have deep, stout, slightly hooked bills. Those in areas with lots of pinyon pine have long, shallow, pointed bills. The shape of the bill helps the jays open their preferred foods: a stout bill is good for hammering open acorns and the hook helps rip off the shell; a thinner, more pointed bill can get in between pine cone scales to get at the pine seeds.

While the Western Scrub-Jay’s broad diet of mainly arthropods and nuts is similar to those of its sympatric relatives, it tends to frequent drier, hotter, and more open habitat and is typically found at lower elevations than the other species. Birds in interior populations are paler and more shy than coastal birds, which are darker in color and more bold in behavior.

Western Scrub-Jays are typically monogamous, and nest in shrubs or low trees. Both members of the pair help build the nest, which is a thick-walled cup made of grass, twigs, and moss, lined with soft rootlets and hair.

The Western Scrub-jay, Aphelocoma californica, with several of its current subspecies and hybridizations is possibly more than one distinct species; a Pacific species of the west, and another east of the Rocky Mountains (including Florida); with each group containing several subspecies more genetically distinct. (See Systematics here.)

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